1. Field of the Invention
The invention relates to a transmitter, in particular for mounting on the head of a process thermometer, having an upper part, a lower part, at least one connection unit and at least one electric contact element, wherein the connection unit is arranged on the inside of the upper part and can be electrically contacted via the contact element from the outside of the upper part. The invention relates further to a method for producing such a transmitter, wherein the electric connection element is arranged on the inside of the upper part and the contact element is arranged on or in the upper part so that the connection unit is electrically contacted via the contact element.
Transmitters of the type mentioned above have been known for a long time, in particular in the field of process measurement technology, here, particularly, for temperature measurement, wherein the field of application of transmitters is not limited to temperature measurement. In general, transmitters have the task of converting a sensor signal into a standardized signal regardless of whether it is a sensor signal from a thermal element, a capacitive or inductive sensor or, for example, the “signal” from a resistance strain gauge (value of resistance) and of providing it to the higher-ranking process control. In the following, the application and use of a transmitter is described using the example of a process thermometer, wherein it is to be asserted that a transmitter is, naturally, not limited to this application.
2. The Prior Art
A transmitter of the type in question is normally arranged in a connecting head, which protects the transmitter from environmental influences and represents a safe assembly alternative for the transmitter. Using wiring, the transmitter is connected to the actual sensor element in the connecting head. In the case of temperature measurement, the thermal sensor element (temperature-dependent resistance or thermal element) is arranged in a thermowell that comes into contact with the actual process and the sensor element is further connected to the connecting head via a process connection and a neck pipe. The sensor element converting the actual physical parameter of interest into an analyzable parameter is normally electroconductively connected to the transmitter via one or multiple contact elements, wherein the contact elements are electrically connected to the connection unit of the transmitter.
Transmitters of like kind consist of an upper part and a lower part, wherein the upper part and the lower part form a hollow space in which the connection unit is found in the assembled state of the transmitter. The hollow space is then, normally, filled with silicone or a compound containing silicone that surrounds and protects the connection unit. A disadvantage of this arrangement is that the transmitter consists of relatively many parts and the production of such a transmitter takes a very long time —due to its construction and the materials used. A significant reason for this is that the silicone used is often of two components and, after the mixing step, the workable silicone compound needs to first be vacuum treated to remove enclosed air bubbles. Furthermore, the silicone used has to be set using a very complex heat treatment process.